Lots of old willies rigs have copper fuel lines. Lots of all the old vehicles had copper for that matter. I think they switched simply because of the cost of copper went up. I know the 62 CJ5 that I have in the shop right now is all copper.

I just learned about this in class today. dont use it with electric pumps or alcohol. Electric pumps work harden the copper through the pulses and alchol corodes it. did here anything bad about it on carbs though. I ran it on my delta 88(injected) for a few months before it broke in half(car not lines) with no problems